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By Pierre de P. Ricketts

Having had occasion while in Europe during the past summer to visit some of the foreign mints and assay offices connected with the same, I thought a brief description of the general process of coining employed, and such items connected with assaying as were new, might prove interesting to the Institute. The principal foreign mints are: the Royal Mint, London; and the mints in Paris, Brussels, Utrecht, Berlin, Vienna, Copenhagen, St. Petersburg, Stockholm, Madrid, Milan, Rome, and Constantinople. My time only permitted my visiting a few of the principal and largest given in the list, and for a description of the remainder I am indebted to the kindness of Mr. James M. Napier, who in company with the deputy master, and chemist of the Royal Mint, made a complete inspection of all the European Mints in 1870.

By K B. Quast

Changes in feed size distribution can have significant effects in rod mill grinding. The product sizing resulting from wet batch milling of a tin ore showed little influence on fines production after truncating the feed at either the coarse or fine end. The addition of fine material caused a less amount of fines to be produced and a possible increase in grinding at coarse sizes, although this is complicated by the changing feed size distribution. The changes in feed size distribution caused no tendency for preferential grinding of the cassiterite.

Jan 1, 1998

By Alichurch P. D

Perseverance nickel deposit is located at latitude 27¦ 491S, longitude 1200 42'E, 330 km north of Kalgoorlie, Western Australia. Gossanous outcrops were discovered in April, 1971, and after further detailed surface investigations, percussion drilling led to diamond drilling by June, 1971. Up to December, 1972, 127 diamond holes totalling 45,590 m were drilled to indicate 33 million tonnes averaging 2.2% Ni using a 1% cut-off grade. The deposit occurs in a lenticular ultra- mafic unit emplaced in metasediments locally forming the eastern flank of the Archaean green- stone belt trending NNW from Leonora to Wiluna. To the east a major strike fault separates the metasediments from gneiss; westwards there is a sequence of metavolcanics with further ultra- mafic units. Length of the lens is 3500 m and it attains a maximum width of 800 In. The eastern contact is moderately regular, but the western contact is prominently embayed. Local strikes are NNW, and dips are steeply W. A set of strike faults cuts the ultramafics and enveloping quartzites. These are normal faults, parallel to the major eastern fault, dipping 65-70¦W. They impart a serrated pat- tern to the sub-outcrop of the western contact. Massive serpentinite is the dominant rock in

Jan 1, 1973

By Thomas L. Kesler

IF all of the 14 million tons of kaolin produced in Georgia through 1949 had been mined from a single deposit 20 ft thick, it would represent a mined-out area of less than 1 sq mile. This measure of depletion is in such strong contrast with the large size of the area shown in Fig. 1, from which most of the output has come, that there has developed an optimistic outlook concerning future supplies of kaolin equal in grade to that already mined. Dozens of mines are widely but not evenly distributed within this area, which consists mostly of parts of Twiggs, Wilkinson, and Washington counties. There are scarcely half a dozen kaolin mines elsewhere in the state that have been appreciably productive, although the areas in which they occur may have good possibilities. Most of the efforts to find new deposits, therefore, will be confined to the area shown in Fig. 1, for it is here that the industry has established its facilities, and prospecting is encouraged by relatively numerous outcrops and opened deposits of kaolin.

Jan 10, 1951

By Dario Libano

"The Line 5 Extension, in Sao Paulo, Brazil, is currently the most important investment in public transportation by Sao Paulo’s state government. It will connect the south part of the city to the city center, crossing through four other major Metro lines and stations; all currently in operation. The total extension of the line is 11 km (6.8 mi), and includes a new parking yard for the trains and 11 new stations. The Brooklin Station, one of the new stations due to be open and operating in 2016, has a unique geometry of five secant shafts.The original design included constructing five secant shafts stabilized by two plastic slurry walls using conventional grab technology. One slurry wall, along the Santo Amaro Avenue, was to contain the contamination plumes, and another was for temporary support to enable the excavation of the shafts. The final retaining wall design was changed to a concrete structural diaphragm wall that reduced the construction time of the shafts by half, allowing the contractor to meet the construction schedule. This solution also avoided dewatering effects in a geological region characterized by Quaternary sediments and environmental contamination plumes. It was the first time that a hydromill was used in such a situation in Brazil. The hydromill, by overcutting the panels, increased the quality of the joints, and decreased the probability of having seepage into the shafts. The hydromill also created a seepage barrier and avoided movement of the contaminated plumes.The GeologyLocal geology is composed of a superficial Quaternary soil, basically soft organic clays and sands and gravels. From the depth of 8 m (26 ft) until 18 m (59 ft), geology is composed by tertiary medium compact sand with thin silt-clay layers. From 18 m (59 ft) down, there are alternations between compact silt-sands layers with very hard clays layers. Each is approximately 5 to 10 m (16.4 ft to 33 ft) thick.The Initial Basic DesignThe original basic design of the Brooklin Station was to be constructed from five 40 m (131 ft) diameter intersecting circular shafts, all in a line along the axis of the Metro tunnel, in 555 days. In the excavation sequence, the odd shafts were first excavated, waterproofed and had part of their inside cast-in-place structure built before the even shafts were excavated. During the excavation of the even shafts, part of the odd shaft’s support was demolished and connected with the even support. A 0.8 m (2.6 ft) thick plastic slurry wall, acting together with the wire mesh reinforced shotcrete support, ensured the excavation stability around the five shafts."

Jan 1, 2014

By Dianne M. Lapierre

Mining firms in Canada are increasingly incorporating the social and environmental interests of their stakeholders into their projects in an effort to become more sustainable. Such initiatives have included negotiating Impact and Benefit Agreements (IBAs) directly with would-be impacted, often aboriginal, communities near resource developments in the Canadian north. Why does a mining firm take on this extra time-and cost-intensive initiative when governments and regulatory measures are in place to address social and environmental issues? Past research has paid little attention to the corporate rationales for IBAs. Based on document review and interviews with mining executives, this study investigates the rationales of mining firms that ?over-comply? with legislative requirements by negotiating IBAs or similar types of agreements with communities. The results indicate that mining firms increasingly recognize IBAs as an intrinsic part of the permitting process. When queried, executives regularly identified the negotiation of agreements as ?the right thing to do?. While this response could be read in ethical terms, a commercial rationale is also clearly present. By building strong relationships with nearby communities, addressing community concerns, and directing benefits to local people, all of which are explicitly achieved with an IBA, mining firms are maintaining their long-term financial viability, thus their sustainability, within an evolving industry.

May 1, 2008

By Charles K. Rose

The Cebolla Creek titaniferous iron deposits near Powderhorn in southern Gunnison County, Colo., were examined by the Federal Bureau of Mines as part of an overall program to investigate the Nation's titanium and iron resources. The deposits occur around the periphery of the Iron Hill stock, which underlies an area of about 12 square miles. Concentrations of magnetite, ilmenite, and perovskite arc localized along fractures in the pyroxenite stock. Mineralogical studies of composite surface samples collected in 1956 showed that most of the iron is present in ilmenite-bearing magnetite. Perovskite is the chief titanium mineral in the magnetite-rich and augite-rich types, and sphene is the principal titanium mineral in the placer material. The mica-rich rock contains approximately equal amounts of perovskite, ilmenite, and sphene.

Jan 1, 1960

By Vsevolod Krivobok

THE re-crystallization of metals has been the subject of much scientific investigation, some of which has resulted in a better understanding of this extremely important and interesting phenomenon. Unfortunately, while many have propounded theories of re-crystallization, but a few have presented experimental evidence as to how it takes place. If this can be determined the question, why re-crystallization occurs, may be answered more definitely. Re-crystallization in single phase metals consists of a complete rearrangement and re-sizing of the grains, of which the structure is composed, while the type of structure remains the same. That is to say, if the structure before re-crystallization is composed of a number of polyhedral grains of different shape and size, a particular spot after re-crystallization will be seen to consist of grains in no way different from the original except in size and shape. The re-crystallized grains may be smaller or larger, depending on the treatment received; and, while the re-crystallization may be brought about by means of heat treatment only in passing through a critical range, yet it is common knowledge that single phase metals subjected to cold working are possessed of a tendency toward re-crystallization, even if the heating does not reach critical range. The study of re-crystallization would, of course, be much easier if we had single crystals of any metal as the original material with which to study the phenomenon of re-crystallization, since it would permit the observation of structural changes at what amounts to enormous magnification, by changing the scale of the specimen. In metals of more normal grain size the crystal boundaries introduce complications, but the process, it may be assumed, is essentially the same. Such an opportunity

Jan 2, 1926

By Jing Zhou

In view of the state of the long time use of sodium cyanide in lead-zinc-sulfur-silver multimetallic ore production, we propose alternative reagents system through experimental research. The experiment first used TJ, sodium sulfide to adjust the flotation pulp, after that, zinc sulfate, sodium sulfite was added to low alkaline pulp to inhibiting zinc sulfur mineral and adapted MB, 25# aerofloat and diethyl dithiocarbamate combination collectors to float lead minerals. The obtained test index is as follows: lead concentrate recovery rate of small scale test was increased by 5 to 10%, the recovery rates of gold and silver in lead concentrate were increased by 7% and 11% respectively; the industrial test is conducted under the condition that the total grade of lead and zinc content in raw ore decreased by 4.81%, the total recovery rate of lead and zinc increased by 7%, recovery rates of gold and silver in lead concentrate were increased by 7.62% and 9.65% respectively. So it successfully realizes the target to replace the sodium cyanide, using low-alkaline non-toxic reagents system in mineral processing practice of three kinds of complex lead-zinc-sulfur ore of this mine. Keywords: refractory lead-zinc-sulfur ore, depressant, non-cyanide flotation

Sep 1, 2012

By Robert S. Penczak

Red Lake Gold Deposits ? Descriptive Classification (modified from Pirie, 1982) VHR Au -- Volcanic-hosted (vein & wall-rock) replacement Au deposits ~93% of camp production Q-(T) Au -- Quartz-(tourmaline) vein Au deposits ~7% of camp production Quartz-sulphide Au deposits Porphyry-hosted sulphide Au deposits Current & Significant Past Producers Camp Production 21.6 M oz / 672 tonnes Au Other Deposits / Occurrences (Intermittent Exploration

Apr 1, 2005

By E. Engelbrecht

"A pressure non-oxidative leach is employed at Anglo American Platinum Base Metal Refiners to extract nickel from a slow cooled matte. The design base requires two 80 m3 autoclaves in parallel to achieve a nickel extraction of 60% at the nameplate capacity of 32.4 ktpa nickel plated. Isothermal modelling of mineralogical and chemical concentration profiles, through a reactive mass balance, permitted rate constant parameter estimation and selection of the most probable reaction pathway. The model was validated with plant data up to a capacity of 26 ktpa Ni plated and suggested by extrapolation that nameplate capacity may be viable through one 80 m3 autoclave.INTRODUCTION Anglo American Platinum Base Metal Refiners is situated on the outskirts of Rustenburg in the North-West province of South-Africa. The refinery produces nickel cathode, copper cathode, cobalt sulphate powder, covellite rich copper pressure leach residue and bulk sodium sulphate through an integrated circuit that refines slow cooled converter matte. The converter matte is milled, non-magnetics are separated as solid nickel copper matte (NCM), and the magnetics are leached yielding a pressure vessel liquor (PVL). The remaining solid platinum group metals (PGM) concentrate after leaching is sent for downstream processing in the Precious Metals Refinery (Hofirek & Kerfoot, 1992). The work presented here is applicable to the base metals refinery which receives the two base metals feed stocks NCM and PVL. In 2009 the capacity of the refinery was upgraded from 21 ktpa nickel cathode plated to 32.4 ktpa. This paper deals with evaluating the capacity of the pressurised non-oxidative nickel leach (NOX) process which accounts for at least 28% of the nickel leached from NCM by design. The NOX design base requires two 80 m3 autoclaves divided into four compartments operated in parallel at 155°C and 600kPa(g). Elevated temperature is required to speed up the leach kinetics of particularly nickel and iron which are trapped in slow leaching mineralogical phases namely millerite and bornite, (Dinham, 2006). The stated equivalent capacity for the NOX configuration was 32.9 ktpa nickel plated at first pass nickel and iron leach efficiencies of 60% and above 80% respectively and is a key step for the selective removal of iron (Bryson, Hofirek, Collins, Stiksma, & Bereaowsky, 2008)."

Jan 1, 2017

By E. J. Lintner

This paper is one of a series being prepared by the United States Bureau of Mines describing clay mining, crushing and grinding methods, and costs, at various operations throughout the United States. These papers are designed to disseminate technical information regarding methods used. The, cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs may in many instances cause embarrassment to the individual operator as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulation shall ensue. The following report deals specifically with the methods employed by the Evans Pipe Co., Uhrichsville, Tuscarawas County, Ohio. The author wishes to acknowledge the assistance of the following company officials: T. J. Evans, II, president; T. J. Evans III, vice president and general manager; and L. P. Young, general superintendent.

Jan 1, 1936

By W. W. Adams

[The s1xteeilth an.nual National Safety C mpeti t1on, concluc ted "by the Bureau of t4ine g, Un+ ~ed st tag' DepartIilent 0:1' the Interior, has jast been closed, and the results reveal t:'W.t. t_!e co~)eting comps.nies had fewer a.ccidents in proportion to the number. of !\1a..."1-h(J1J.l'~ :orkcd than in a:ny other yeex in the record of the contest. These annUk~l contestn are thus achieving the r purpose of promoting safety in tho minin induC'tr:r. ]

Jan 1, 1941

By Wing G. Agnew, Paul L. Russell

"INTRODUCTION During the past few years, the development of millisecond-delay electric blasting caps has made possible a more flexible control over timing the firing of individual charges in blasting, The use of these caps has proved especially productive in quarry blasting and in numerous construction operations, but their use in underground mining is developing more slowly, although in some cases, as the solution to a difficult breaking problem, they have been well-received. When used in metal-mine drifts, the general objection is that the broken rock is thrown too far. In nearly all cases, however, use of millisecond-delay caps results in better fragmentation of the rock and a lower powder consumption per ton of rock broken.Prom 1949 to 1952, several series of experiments were conducted at the Mount Weather, Va., Experimental mine in conjunction with driving a 6- by 10-toot ventilation raise. 3/4/ The raise-round experiments in this 238-foot shaft, using millisecond-delay electric blasting caps in various drill-round patterns, are the subject of this report.SUMMARY AND CONCLUSIONSAll rounds discussed in this report were drilled in the hard rock (epidosite and greenstone) of the ventilation raise at Mount Weather Experimental mine (figs. 1 and 2). The drill-round patterns varied from 28- to 32 holes and from a V-cut design to one having no cut boles at all. With the exception of the first two rounds, all blasting was done with millisecond-delay electric blasting caps. In all rounds 60-percent ammonia gelatin dynamite was used and holes were stemmed with two cartridges of sand stemming."

Apr 1, 1953

By Ernest E. Fairbanks

[Microscopic methods have proved to be valuable assets in the study of low-grade ores. While the chemical assay u a ally discloses tine total content of valuable metals in such an ore, a thorough knowledge of the nature of the ore should form the from which to prepare an efficient means of recovery. In the treatment of low-grade ores, inefficient recovery, as indicated bay the amount of valuable mineral permitted to go to waste in the tailings, is too frequently the rule rather than the exception, As methods of recovery become more efficient, many low-grade 10 mineral A posits suddenly assume o commercial significance, In much of this material the minerals are so finely disseminated and intermixed that identification even by microscopic methods is a difficult matter. The application of microchemical qualitative analysis with the aid of new device described in this paper, will solve many of the problems of identification encountered in the study of low-grade potential ores. In these ores, especially, the limitations of ordinary microscopic methods are liable to become very great. The microchemical tests obtained by applying a standard set of reagents to a polished knoting whether or not a tarnishing action develops, have considerable value but arc far from being infallible. It is well-known that electrolytic effects are apt to affect seriously the diagnostic value of the tests, end this effect is encountered much more frequently in dealing with finely desseminated minerals. resort to microchemical qualitative analysis, therefore, becomes indispensable.]

Jan 1, 1924

By Glaser. C., J. Balz, F. Logsch, R. Heiduschke, M. Leiker, P. Ay

The treatment of iron-hydroxide-containing water from ground water and surface water is achieved by a combination of the process steps of flocculation and subsequent mechanical dewatering. The aim is to create solid pellet structures by extending the structure forming flocculation process with a build-up pelletizing process which can be transferred directly into a drying unit. A Taylor-Couette-reactor (diameter of the inner cylinder – 40 mm, gap width – 5 mm) was used for these experimental studies. To produce the necessary flow profile the inner cylinder was rotated at a speed of 230 rpm. The iron hydroxide-containing suspension (dry matter content: 2 mass %) was added simultaneously with the addition of a cationic high-molecular flocculant in various flocculant dosages and residence times of 5 to 15 min. The pellets were examined for parameters such as geometric dimensions, dry substance content and dewatering behaviour. As the results show, there is a direct relationship between the residence time and the geometric dimensions of the pellets. After a residence time of 5 min, round pellets with an average diameter of 6 mm were formed. With an increase in the residence time up to 15 min, a compaction of the pellets could be observed, which resulted in an increase in the dry substance content of 8.0 to 11.2 mass % on average. After completion of the pelletizing process, the pellets were mechanically dewatered by filtration. By applying this innovative wet pelletizing of iron-hydroxide containing suspensions in a Taylor-Couette-reactor, it is possible to carry out the process of flocculation combined with the pellet formation with simultaneous pellet compaction in a single process step. The resulting pellet structures are distinguished from conventional floc structures by an improved water discharge capacity. After classification the pellets can be marked directly as easy-to-handle bulk material, suitable as feedstock in percolation columns for the purification of contaminated fluid streams

Jan 1, 2018

By S. K. Sahoo, S. K. Sharma, A. Yadav, B. Behera, G. S. P. Singh

A field representative modeling of the gob behavior is critical for the understanding of the associated mechanics of strata behavior in longwall workings. The findings of theoretical models and laboratory tests on the simulated gob material have shown the strain hardening behavior of the gob material. The double-yield material model, which is a built-in constitutive model in FLAC3D, has significant potential to simulate the gob compaction process as it represents materials which undergo irreversible compaction in addition to shear yielding. Apart from this, several researchers have attempted using modified elastic model or applied nodal force in reaction to the strain in the gob area as per the well-known theoretical relations to meet this requirement. Although these models can simulate the mechanical response of the gob for subcritical and critical extraction widths, they do not apply to supercritical extraction width as the gob stress may exceed the in situ stress level in such cases. For overcoming these limitations, a standard approach has been developed and validated in this paper, which can be used for simulating the gob behavior in supercritical longwall workings as well. The complete study is divided into two stages wherein the laboratory scale compression test on the simulated gob material has been numerically replicated to develop preliminary confidence followed by a parametric study of the double-yield constitutive parameters for a rational estimation of their values in different conditions. The calibrated model has been used for verifying its results by plane strain modeling of two different longwall workings, using well-established empirical and analytical findings and field observations. The approach suggested in this study can be used for the efficient modeling of the gob behavior of longwall panels under varying geo-mining conditions without compromising the accuracy of the numerical model. The meticulously validated model can be helpful in rational estimation of stress redistributions around the gob area apart from load transfer on the barrier pillar.

By Fred C. Bond

AN improved method of measuring the surface area of a comminution product down to any desired particle size has been developed. The method is largely graphical, and requires relatively little calculation. It can be used with materials containing large amounts of clay, or excess fines of any kind. The surface area S is expressed in terms of square meters per 100 c.c. of solids. This expression is based upon volume rather than weight, and is considered to be more suitable for crushing and grinding problems, where the machines ordinarily are operated under constant volume conditions. It has the advantage that surface areas of different materials can be compared directly, even though their specific gravities may be unknown. The "specific surface" of a material, or the number of square centimeters of surface area per gram, is equal to 100S divided by the specific gravity. Particle diameters are expressed in microns, K being the diameter of the largest particle present and L the grind limit, or lower size limit of the particles formed directly by grinding. The value of K does not always coincide exactly with the diameters of the largest particles retained on the coarsest testing sieve, since the largest particles formed in crushing and grinding are often slabby, or have other irregular shapes. L has been chosen as 0.700 microns, or number 27.5 in the size number series, for reasons to be explained later. S is the total surface area of all particles larger than L microns in diameter. When a homogeneous comminution product is separated into fractions whose diameters bear a constant geometrical relationship p to each other, and the log per cent weight retained upon each size and passing the next larger size is plotted against the log diameter, a straight line results, which is called the distribution line, and which has a slope in called the distribution modulus. The distribution line can be extended to any desired limiting size, and the total surface area of all particles larger than that size can be calculated. The equation of the distributi0n line is [w = Cx" [I]] where w is the per cent weight retained on each successive sieve; x is the particle diameter; and C is the per cent weight retained on an opening of unit diameter.2 Theoretically, the distribution line can be extended to include infinitely small particles. When it is so extended, and the assumption is made that no fine particles are present other than those accounted for by the equation; the log per cent cumulative weight passing any series of sizes, plotted against the log diameter passed, will result in a straight line lying parallel to and above the plotted distribution line.

Jan 1, 1941

By A. G. Guy

IN the course of a research on steady-state diffusion it became necessary to make diffusion calculations for a finite solid. This problem was found to be sufficiently different from the corresponding problem for the semi-infinite solid for an entirely new approach to be necessary in obtaining a useful solution. The assumption of an exponential variation of the diffusion coefficient with concentration' was no longer a practical necessity, so that the new solution offered the possibility of handling diffusion in semi-infinite solids for arbitrary variations of the diffusion coefficient with concentration. In discussing the principle on which this method of calculation is based, it is convenient to consider the relatively simple problem of one dimensional diffusion into a matrix that initially contains none of the diffusing substance. The solution of the set- ond Fick Law,?C/?t=D0?2C/?x2, for diffusion into a semi-infinite solid is3 C/C=1-F(x/2vD0t [1] where C is the concentration of the diffusing substance at a depth x cm below the surface after dif- A. G. GUY, Member AIME, and M. GOLOMB are Professor of Metollurgicol Engineering and Professor of Mathematics, respectively, Purdue University, Lafayette, Ind., A. S. YUE, formerly with Purdue University, is now with the Research Laboratory, Dow Chemical Co., Midland, Mich. TP 4505E. Manuscript, July 18,1956. fusion has occurred for t seconds; C, is the concentration of the diffusing substance at the surface of the matrix; Do is the diffusion constant, expressed in sq cm per sec; and + represents the Gauss error function. The corresponding solution for diffusion into a finite solid of thickness, 1, is conveniently written for the change in concentration, C+, at a point midway through the matrix and for times, t, great enough for the following equation to be used4 c1/2/C1=(1/2-2/?e-?2D0t/l2) [2] In Eqs. 1 and 2 the diffusion coefficient is represented by the symbol Do (rather than by D) to emphasize that these equations are valid only for constant values of D. To understand how these equations can be modified to take account of actual variations of D, such as that shown in Fig. 1, first consider the fact that for a given time of diffusion theconcentration at a given point is determined, not by the D value alone, but by the ratio x/vD0 in Eq. 1 and by a similar ratio, l2/D0 in Eq. 2. Even though in fact D varies, it is possible to keep this ratio constant by using a special coordinate system, x,, that varies with D in the appropriate manner. The necessary character of this special coordinate system can be easily visualized by imagining that

Jan 1, 1958

By W. C. Phalan

"Prewar Conditions:Metallic magnesium may be considered a war metal, but a war metal with a future, so far as the industry in the United States is concerned. Its production in the United States prior to 1915, on a commercial scale, was negligible, but imports prior to that year may be taken as a gaze of the demand for the metal. Unfortunately, magnesium was not listed separately by the Department of Commerce prior to the war, among the importations, but was included with other metals, as follows: ""Barium, calcium, magnesium, sodium, and potassium, and alloys of which said metals are the component materials of chief value."" However, the imports of metals enumerated other than magnesium were probably small, so that the importations under the above caption may be considered chiefly metallic magnesium in one form or another and, therefore, is an approximate gage of the demand for the metal in the United States. These imports were as follows:These figures are so close that they give a good idea of the figures for the respective calendar years.Of this prewar use, it has been estimated that about 85 per cent was used annually and in approximately equal quantities in the production of (1) flash-light powder, (2) fire works, (3) aluminum casting work, and (4) nickel and nickel-copper alleys, such as monel metal, etc. The re¬maining 15 per cent was employed for general uses, such as deoxiding brass and other copper alloys in foundry work, and to a small extent in laboratory and research work."

May 1, 1920